Magnetic core circuit for indicator tube



Jan. 23, 1968 RjYll I 3,365,611 MAGNETIC com CIRCUIT FOR INDICATOR TUBE Filed July 1, 1965 Q 5 a? E 8% Q \g/ :2

INVEN'FU Q 'T'TUR'NEIQ/ United States Patent 3,365,611 MAGNETIC CORE CIiCUIT FOR INDICATOR T BE Roland Yii, Far Hiils, N.J., assignor to Burroughs Corporation, Detroit, Mich, a corporation of Michigan Filed .iuly 1, 1965, Ser. No. 468,861 7 Claims. (Cl. 31584.6)

ABSTRACT OF THE DISCLOSURE The disclosure is of a circuit for operating a biquinary indicator tube which includes two sets of glow cathodes, each having its own operating anode and connected in pairs, with each pair including one cathode of each set. In operation of the tube, operating potential is applied to a pair of cathodes, and one selected cathode of the pair is caused to glow by applying operating potential to the associated anode. A magnetic core switching circuit is provided for each anode, and an oscillator is connected to both switching circuits for switching them on and oii alternately and thus applying positive and negative operating potential alternately to the anodes. Each magnetic core ci c it includes an inhibit winding which is used to inhibit one switching circuit and permit the other to operate the anode associated with the glow cathode selected by the input information signals. The input information signals include signals for selecting a pair of cathodes and inhibiting one anode.

This invention relates to electronic control and driver circuits for indicator devices, particularly for gaseous cathode glow tubes.

The principles of the invention relate particularly to a circuit which uses a gaseous indicator device of the type known as a biquinary tube and useful in circuits operating with biquinary logic. This type of indicator tube includes two groups of glow cathode indicator electrodes, with each group having its own anode electrode. In operation of this tube, the cathodes are connected in pairs with each pair including one cathode from each group, and, when a signal is applied to a pair of cathodes, the desired one cathode is selected and caused to glow by the application of a suitable selecting potential to the proper anode electrode. This type of indicator tube is, relatively speaking, a high voltage device and usually requires a power supply of the order of 200 volts for its operation. Thus, since high voltages are required for the tube, certain driving circuits which use transistors require high voltage transistors for their operation. Such transistors and circuits are relatively expensive, and it is generally preferable, if possible, to operate with low voltage circuits of maximum simplicity.

Accordingly, the objects of the invention concern the provision of an improved driver circuit for a cold cathode indicator tube, particularly a tube such as a biquinary tube, the circuit being operable with a relatively low voltage power supply and with low voltage semiconductor devices and other components.

Briefly, a circuit embodying the invention is used to drive a biquinary indicator tube of the type described above, with the circuit providing information signals to each pair of cathode electrodes and with switching or selection signals being applied to the proper anode electrode. The circuit for selecting the proper anode includes a square hysteresis loop magnetic core associated with each anode. A square loop core has at least two stable operating states. An oscillator is provided having two output windings, one on each core, and each output winding is coupled to one anode of the indicator tube. Each output winding anplies high voltage pulses to its anode 3,365,611 Patented Jan. 23, 1968 as its core is switched back and forth between its two stable states. These voltage pulses are of sufiicient magnitude to cause a cathode to glow. Each core is also provided with an inhibit winding which is coupled to a control circuit therefor. The control circuits control the operating state of the cores, and thus, they control the application of glow-producing potentials to one or the other of the anode electrodes.

The invention is described in greater detail by reference to the drawing wherein the single figure is a schematic representation of a circuit embodying the invention.

The circuit of the invention includes magnetic cores which have rectangular or square hysteresis loops and can be operated in two stable states, one a state of maximum positive magnetic remanence known as the set state, and the other a state of maximum negative magnetic remanence known as the reset state. Each core carries a plurality of windings, and the dot convention is used to show the operating relationship between the various windings on a core. By this convention, current into the dot end of a winding tends to set the core, and current out of a dot end tends to reset the core. In addition, current flow into the dot end of one winding on a core induces current flow out of the dot end of the other windings on the same core. Thus, the voltage induced at the dot end of a Winding will be the opposite of that induced at the nondot end of the same winding.

The circuit 10 shown in the drawing is a decoder circuit and converts binary-coded decimal signals to decimal si nals by means of biquinary logic. The decoded output decimal signals are displayed visually by a display device 16 which is a gaseous glow cathode indicator tube of the type known as a biquinary tube. This type of tube, which is shown schematically in the drawing, includes ten indicator cathode electrodes 20 which comprise numerals 0 to 9. These cathode numerals are arranged in two groups 24 and 26, with one group 24 including the evennumbered cathodes O, 2, 4, 6, and 8, and the other group 26 including the odd-numbered cathodes 1, 3, 5, 7, and 9. Of course, some grouping other than odds and evens could be used, if desired. The cathode electrodes are also connected in pairs, with one cathode in one group being connected to one cathode in the other group, with successive numbers usually being connected as pairs. The indicator tube 16 also includes anode electrodes 28 and 30 associated one with each group of cathode electrodes, and each anode is used to cause the cathode electrodes in its group to glow.

One suitable logic circuit for applying decimal signals to the pairs of cathodes includes a source 34 of four-bit binary-coded decimal signals coupled through eight lines to a suitable decoder 36 which has seven output lines, five of which are signal lines 38 and carry signals having a decimal representation, and two of which are control lines 40 and 41 and carry control signals. Each signal output line 38 is connected to a pair of cathode electrodes in tube 16.

The decoder circuit 10 includes a driver or selection circuit 50 coupled to the anode electrodes 28 and 30 in the indicator tube 16 to select the proper anode for each group of input signal 'bits which is decoded and applies a signal to a pair of cathode numerals 20. The driver circuit 50 comprises an oscillator 60 which may be of any suitable form. The oscillator shown includes two semiconductor devices such as triode transistors 64 and 66 which have their emitter electrodes 68, 68 connected together and to a source of reference potential such as ground potential, and their bases 70, 70 and collectors 72, 72 cross-connected. In addition, the collector electrode 72 of transistor 64 is coupled in series through a first winding 8:} on a first magnetic core 82 and a second winding 83 on a second core 84 to a suitable positive DC. power source Va. The collector electrode 72' of transistor 66 is similarly coupled in series through a winding on the first core 82 and a winding 94 on the second core 84 to the power supply Vc. With these connections, the oscillator 60 alternately sets and resets both cores in each cycle of its operation.

Core 82 is also provided with an output winding 190 which has one end connected to ground potential and the other end connected through a diode 184, oriented as shown, to the anode electrode 28 in tube 16. The other core 84 also has an output winding which is similarly connected through diode 114 to the other anode 30 in tube 16. As the oscillator drives the cores 82 and 84 through a switching cycle and switches the cores between their two stable states, the cores generate first positive and then negative voltage pulses in both ouput windings 100 and 110. These positive and negative voltages are applied at the same time to both anode electrodes 28 and 30, and, when a suflicient potential difierence is present between an anode electrode and an associated cathode elec trode (due to signal from decoder 36), then the cathode exhibits cathode glow.

According to the invention, each core is also provided with means for selecting one core or the other to operate a selected anode electrode and thereby to cause a selected cathode electrode to exhibit cathode glow when a pair of cathodes receives an information signal from decoder 36. In one suitable selection circuit for operating the inhibit windings, the winding is connected between the emitter and collector of an NPN switching transistor 150, and the winding 124 is connected between the emitter 130 and collector 140' of an NPN switching ransistor The emitters of the transistors are connected to ground, and the bases or input elecrodes 154, 154 are copuled through resistive paths to a suitable bias source Vb. In addition, base 154 is connected through a resistive path to decoder control line 40, and base 154 is connected through a resistive path to decoder control line 41.

In operation of the circuit 10, with no information signals applied to tube 16 from decoder 36 and with the inhibit windings 120 and 124 inoperative, the oscillator 60 first sets and then resets both cores 82 and 84 in each cycle of operation. The cores and output windings 100 and 110 are designed and arrayed so that each time the cores are set, they generate positive voltage pulses of about 85 volts which are applied to both anodes 28 and 30 of tube 16. This provides insuflicient voltage between the anodes and the cathodes to cause a cathode to glow. When a group of signal bits is applied to the decoder 36, a generally negative signal having the proper corresponding decimal representation energizes one of the lines 38' coupled to the pair of cathodes which includes the proper decimal numeral. Assume that the decimal signal represents numeral 2 and is applied to paired cathodes 2 and 3. In the circuit shown, the decimal information signal on line 38 is a generally negative signal. At the same time, line 40 carries a proper control signal to switch on transistor 150 and operate inhibit winding 124 and thus inhibit core 84 and prevent it from switching. Thus, only core 82 can switch, since its inhibit winding is not operated, and it applies positive pulses to anode 28. These positive pulses combined with the negative decimal signal applied to cathode numeral 2 are of sufiicient magnitude to cause cathode 2 to glow. Each group of input signals to the decoder 36 provides a decimal signal on a line 38, and at the same time, one of the lines, 40 or 41, carries a control signal to inhibit the proper anode elecrode in tube 16.

Those skilled in the art will understand that the principles of the invention may be applied in circuits other than those specifically described above. For example, it is clear that the input signals to the paired cathode numerals might come from circuits other than decoders,

such as counters or the like. In addition, any suitable arrangement may be employed to operate the inhibit windings on the magnetic cores. For example, any suitable electronic switch or even a mechanical switch could be employed. In addition, signal polarities and pulse magnitudes can be varied or reversed, as desired.

It can be seen that the circuit of the invention requires no steady high voltage power supply suchas that normally required with indicator tubes of the type described above. This advantage is achieved because the relatively high voltages normally required are generated as pulses by the magnetic core circuitry. As an incidental advantage of this type of pulse operation, the life of the indicator tube is increased over what it would be with steady high voltage operation.

What is claimed is:

1. A circuit for operating an indicator tube including 1 a glow cathode gaseous indicator tube containing two groups of indicator glow cathode electrodes and two anode electrodes, each cathode in one group being electrically connected to one cathode in the other group to provide pairs of glow cathodes, and each anode electrode being associated with one group of glow cathodes,

each anode being adapted to energize one cathode of a pair of cathodes when an electrical signal is applied to the pair,

an input signal information source coupled to each pair of glow cathodes to apply electrical signals thereto,

a separate switching circuit coupled to each anode, each adapted to be energized and to apply operating potential to its anode,

an oscillator circuit coupled to said switching circuits and adapted to energize first one and then the other of said switching circuits, and

auxiliary means in each switching circuit coupled to a source of control signals for inhibiting one or the other of said switching circuits from being energized by said oscillator, the uninhibited switching circuit being coupled to the anode associated with the cathode selected by the input signal information.

2. The circuit defined in claim 1 wherein said switching circuits include a pair of magnetic cores, each coupled to one of said anode electrodes.

3. The circuit defined in claim 1 wherein said switching circuits include a pair of magnetic cores, each coupled to one of said anode electrodes, and an inhibit winding on each core.

4. The circuit defined in claim 1 wherein said switching circuits include a pair of magnetic cores, each coupled to one of said anode electrodes, and an inhibit winding on each core, each winding being coupled to and operated by a signal-responsive switch. I

5. The circuit defined in claim 1 wherein said switching circuits include a pair of square loop magnetic cores, each coupled to one of said anode electrodes, and an inhibit winding on each core and coupled to and operated by an electronic switch.

6. A circuit for operating an indicator tube including a glow cathode gaseous indicator tube containing two groups of indicator glow cathode electrodes and two anode electrodes, each cathode in one group being electrically connected to one cathode in the other group to provide pairs of glow cathodes, and each anode electrode being associated with one group of glOW cathodes,

each anode being adapted to energize one cathode o a pair of cathodes when an electrical signal is applied to the pair,

a signal information source coupled to each pair of glow cathodes to apply electrical signals thereto,

a separate square loop magnetic core coupled through an output winding to each anode electrode, an oscillator coupled through a set winding to each core and through a reset winding to each core, and

switch means including an inhibit winding on each core for controlling the application of control signals to said anode electrodes for selectively energizing one anode and thus energizing one cathode of a pair.

7. The circuit defined in claim 1 wherein the input signal information source includes a source of signals, and

a decoder circuit coupled to said source, the output of said decoder circuit including a separate information line coupled to each of said pairs of glow cathodes, and a separate control line coupled to each 6 switching circuit, whereby each combination of input information signals applies operating potential to one pair of cathodes and to one switching circuit associated with the proper anode to be operated to cause the proper cathode of the selected pair to glow.

References Cited UNITED STATES PATENTS 2,912,653 11/1959 Tillman 30788.5 3,307,171 2/1967 Claessen 315-84.6 X

ARTHUR GAUSS, Primary Examiner. I. ZAZWORSKY, Assistant Examiner. 

